A physical therapist tests a patient’s latissimus dorsi strength in prone with the arms at the side and palms facing the ceiling. After the patient lifts the arm through full range, what is the next best step?

• A. Extend the arm while seated without back support
• B. Repeat the motion while turning the palm downward
• C. Repeat the motion while the therapist adds resistance
• D. Extend the arm while in sidelying position with the upper arm supported

Answer: (C)

In manual muscle testing, you first have the patient perform the motion through available range against gravity to demonstrate adequate ROM in the target muscle. The next step is to apply resistance to see how much force the muscle can generate and maintain against an external load, which reveals the strength level. For the latissimus dorsi tested in prone with the arm by the side and the palm facing ceiling, the action is shoulder extension with adduction and internal rotation. After the full range is achieved, adding resistance directly tests how well the latissimus dorsi can sustain or increase that movement under load, which is the most informative way to gauge strength. The other options would change the position, the muscle emphasized, or bypass the resisted portion of testing, so they don’t provide the same clear measure of strength.